1. Field of the Invention
The present invention relates to a method for improving the picture quality of television signals given activity-controlled DPCM coding, wherein an estimated value for the determination of the DPCM signal of a value is calculated from the surrounding video signal values of the current sample and from the video values of the preceding television field surrounding this sample, wherein an activity criterion is identified from the video signal values of the same television field surrounding the current sample and from the video signal values of the preceding television field surrounding the current sample by calculating the amplitude differences, and wherein the estimated value from the video signal values and of the preceding television field is employed given an activity criterion below the first threshold. The invention also relates to a circuit arrangement for realizing the method of the invention.
2. Description of the Prior Art
The picture quality achieved with known DPCM methods is not always satisfactory at low transmission rates of, for example, 34 Mbit/s given two-dimensional calculation of the estimated value. An improvement can be achieved given standing images by the addition of video signal values of the preceding television field (interfield DPCM).
The coding dependent on the activity, i.e. on the contrast between mutually-corresponding picture points of chronologically-successive television signals was investigated in a CCIR document 11/CMTT of the CCIR Study Groups, in the period 1978-1982, Study Program 25A/11 (Mod I), "Getrennte Codierung von Farbfernsehsignalen mit 34 Mbit/s".
This proposed method requires a substantial expense for computation.